Pumping system



A. PETERSON PUMPING SYSTEM I March 19, 1940.

Filed llarch- 30, 1939 Patented Mar. 19, 1940 UNITED STATES PATENT OFFICE I 2,194,054 rumme srs'rm Arvid Peterson, Trenton, N. 1., assignor to De Laval Steam Turbine Company, Trenton, N. 1.,

a corporation of New Jersey Application March '30,

3 Claims.

of a centrifugal pump or compressor, for example, is of a variable speed type such as a steam turbine, eflicient operation will be realized not 18 only at maximum demand, but also under normal operating conditions. I

However, if the speed of the driver cannot be varied, such as in the case of certain kinds of electric motors, as those of synchronous type,

' reduced capacity and pressure can only be obtained in either of two fashions. The first is by throttling the delivery, which action generally results in a considerable waste of power. The alternative, which makes possible more efflcient operation at partial capacities and pressures with constant speed drivers, involves the use of a variable speed couplingbetween the driver and the pump or compressor. Hydraulic couplings of the well known Fottinger type have However, other types of eilicient variable speed couplings may also be used.

It is the" object of the present invention to provide a more effective pumping system in which a constant speed driver such as a synchronousmotor may be used to drive a pump to supply a variable demand. It will be understood hereafter that where reference is made to a centrifugal pump the term may be considered pumps, blowers and compressors for elastic fluids, the invention being applicable generally to the. delivery of fluids to supply variable demands by the use of apparatus the speed of which must be varied to suit the demand. I

The above general object. and more specific objects of the invention, particularly relating to details, will be apparent from the following description, read in conjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic v ustration of a pumping system in which a plurality of pumps are connected in series to provide successive stages for the handling of fluid; and

been found particularly desirable in this use.

as including not only liquid pumps, but also 1939, Serial No. 265,037

Figure 2 is a similar diagram but showing a plurality of pumps arranged in parallel. Referring first particularly to the series arrangement of Figure 1, such an arrangement is particularly applicable in pumping plants in j which the pressure requirements are such that multistage pumps are required. Such pumps have been provided either with all the impellers operating in series in one casing or having separate casings with one or more impellers ineach '10:

casing, the pump casings being connected in series in order to obtain the required pressure. Heretofore, a variable speed coupling has been applied between the electric motor and the single multistage pump or all of the pumps of a series II providing a plurality of stages. What is proposed in accordance with thepresent invention is to apply the coupling in such fashion that part of the pumping unit operates at constant speed and another part at variable speed through Q themedium of a coupling such as a hydraulic coupling having an adjustable slip. This results in additional saving in power of considerable magnitude and also in reduced cost of coupling used; in other words, increased operating efll- Q8 ciency is obtained consistent with reduction in the original investment, which is an unusual con- J dition, the opposite generally being true.-

In the diagram of Figure 1, there is illustrated at ,2 an electric motor which, for purposes of 86 illustration, may be considered as of a synchro nous, and accordingly constant speed, type. The invention, however, is applicable even in the case of variable speed motors such as induction motors, which operate most efliciently at some optimum speed and which involve considerable reduction of efliciency with drop of speed. If an induction motor is used, for example, it may be operated with a minimum of slip, even though the pumping requirements vary greatly.

The motor 2 is illustrated as connected through a fixed coupling 4 to a centrifugal pump 6 the shaft of which is in turn connected to the impeller member 8 of a hydraulic coupling, which may be, for example, of the Fottinger type. The runner member ill of this coupling serves to 'drive a second pump l8.

The Fottinger coupling is well known, and its operation need be illustrated only diagram matically. Essentially, this type of coupling involves contlnuousl leakage of driving liquid through a passage such as I! to a variable pump;- ing means indicated at M by which it is returned through a passage It to the coupling. By so controlling the recirculation of the liquid, the

coupling may be operated containing varying quantities of liquid, with the result that the slip of the two parts may be very small, or may be quite large. These couplings will operate stably even it the runner operates at only about twenty I per cent.'of the impeller speed.

The supply of liquid to the pump 6 is indicated at 20. This first stage pump 6 delivers through a passage indicated at 22 to the second stage pump l8, which in turn delivers its liquid as indicated at .24.

The advantage of the arrangement illustrated in Figure 1 will be readily understood. The design of the arrangement will have to be such that, with the pump I8 operating at full speed and the pump 6 at its constant speed, the maximum demand will be met. The pump 18 in relationship to the pump @may also be such that.

with the pump 18 operating at minimum speed consistent with proper operation of the variable coupling the minimum demand will be supplied. Taking these two requirements into consideration, there can be arrived at the minimum size of the pump l8, from which will follow the proper size for the pump 6.

If this design is used, it will be obvious that both investment and operating advantages will I be secured.

more generally it might be considerably smaller.

Thus, the coupling used need only be of sufficient size to transmit one-half or less of the power delivered by the driver. Not only the coupling, but its auxiliaries as well, for example, the recirculating pump, will be reduced in size. Thus the investment may be cut to a fraction of that requiredin a coupling designed to transmit the entire required power.

Additionally, there is involved a very substantial saving in driving power. Any variable speed coupling of the hydraulic or any other type involves some power loss. The efliciency of a coupling is only slightly dependent on its size, and the entire power loss in the coupling is, therefore, substantially proportional to the power which it is required to transmit. example, that each pump in theillustration is developing the same pressure. With the coupling between the two pumps as illustrated, the coupling would only have totransmit one-half the power and would be subject, therefore, to only about one-half 'the loss as compared with a coupling which would be used to drive both stages. An example will best illustrate .what the coupling between the pumps will accomplish. Assume a unit des ignedlfora maximum demand of 11,100

1 gallons per minute against a1350 foot head. Norits efliciency would be about ninety-six per cent,"

Imal requirements may call for operation at 325 foot head and a capacity range' fisom 5550 to 11,800 gallons per minute. At maximum demand,- the pumps require 1 1105 brake. horse power and with the normal slip in the coupling so that the output from the motor would have to be 1150 horle power corresponding to a loss Suppose, for

in the coupling of 45 horse power if both pumps were driven through the coupling.

As contrasted with the above, and considering the same demands, if only one of two equal size pumps were driven through the coupling and the other driven directly by the motor, the loss would be only 22.5 horse power and the output thermore, the coupling would have to transmit only 552.5 horse power as compared with 1105 horse power in the former case. The cost of a coupling and its auxiliaries is a function or the power required to be delivered and thus, it will be seen, that in the example just indicated the cost of the coupling would be materially reduced. It will be obvious that still greater saving in power and cost of the coupling would be accomplished by designing the pump which is driven through the coupling for less than one-half the maximum specified load. This could be done if the speed variation requirements of the smaller pump could be attained without great loss of efficiency.

It will be obvious that the invention may be embodied in various modifications. For example, the driving motor may well be between the constant speed pump and the combination of variable speed coupling and another pump. The variable speed pump may constitute the first rather than a last stage, or, if more than two stages are used, the variable speed pump may be any one of the pumps. In general, the arrangement will depend ,upon space requirements, etc., but it will be evident that because of the reduced size of the coupling reduction in the space required by the installation will generally result. In fact, by the" use of a nested shafting arrangement, it is possible that impellers constituting different stages may be driven at different speeds, one constant and one variable, within the same casing.

Furthermore, either or both of a plurality of pumps provided in accordance with the present invention may of itself be a multiple stage pump.

Saving in power under certain operating conditions may be accomplished when two or more pumps are connected in parallel with one of the pumps driven at constant speed and the other at variable speed through a variable speed coupling. Such an arrangement is illustrated, for example, in Figure 2, in which the constant speed pump and variable speed pump 18 are connected in parallel, as indicated by the passages 26 and 28 delivering to a common conduit 30.

It will be obvious that various other modifications of the invention may be adopted. In general it may be said that the invention is related to having the variable speed confined to a pump-, ing unit which will be as small as possible so that the power to be transmitted through a variable speed coupling ,will be a minimum.

What'I claim and desire to protect by Letters Patent is:

1; In" combination, a motor of substantially constant speed type, a plurality oi pumps arranged to supply conjoin'tly a variable fluid deinand, means connecting one of said pumps to the motor for substantially constant speed operation thereby, and means connecting another of said pumps to the motor to be driven thereby at variable speed the last named means including a clutch of variable slip type.

2. In combination, a motor of substantially constant speed type, a plurality of pumps connected in series to supply a variable fluid demand,

means connecting one of said pumps to the motor required of the motor 1127.5 horse power. Furiorsubstantially constant speed operation thereby, and means connecting another of said pumps to the motor to be driven thereby at variable speed, the last named means including a clutch of variable slip type.

3. In combination, a motor of substantially constant speed type, a plurality of pumps connected in series to supply a variable fluid demand,

able speed, the last named means including a 5 clutch of variable slip type.

. ARVID PETERSON. 

